It is established that conditions such as sciatica and low back pain are due to activation and irritation of intraspinal nervous structures by disk derived substances (45, 48, 49). One key substance for inducing such irritation is Tumor Necrosis Factor alpha (TNF or TNF-alpha). TNF is a proinflammatory cytokine that may sensitize a nerve root in a way that when it is simultaneously deformed mechanically, ectopic nerve may be elicited locally and interpreted by the brain as pain in the corresponding dermatome. TNF may also induce a nutritional deficit in the nerve root by increasing the vascular permeability leading to intraneural edema, and by initiating intravascular coagulation by activation of adhesion molecules at the surface of the endothelial cells (48). Both these mechanisms may subsequently lead to a reduced blood flow with a reduced supply of nutrients and elimination of metabolic waist products. This reduction in nutrition may also induce sciatic pain per se. TNF may also induce low back pain due to local irritation of sensory nerve endings at the surface of the intervertebral disk. This may occur when the nucleus pulposus herniates out into the spinal canal and TNF produced and released from the disk cells may reach the nerve endings.
Disk herniation is a troublesome disorder, which can cause pronounced pain and muscle dysfunction, and thereby loss of ability to work. A herniation may occur in any disk in the spine but herniations in the lumbar and the cervical spine are most common. A disk herniation in the cervical spine may induce radiating pain and muscle dysfunction in the arm, which is generally referred to as cervical rhizopathy. Herniation in the lumbar spine may induce radiating pain and muscle dysfunction in the leg. The radiating pain in the leg is generally referred to as sciatica. Disk herniation will cause trouble to a varying degree, and the pain may last for one or two months or in severe cases up to 6 months. The arm or leg pain that can occur as a result of disk herniation can be very intense and may thus affect the individual patient's whole life situation during the sickness period.
U.S. Pat. No. 5,703,092 discloses the use of hydroxamic acid compounds and carbocyclic acids as metalloproteinase and TNF inhibitors, for the treatment of arthritis and other related inflammatory diseases. No use of these compounds for the treatment of nerve root injuries is disclosed or suggested.
U.S. Pat. No. 4,925,833 discloses the use of tetracyclines to enhance bone protein synthesis and treatment of osteoporosis.
U.S. Pat. No. 4,666,897 discloses inhibition of mammalian collagenolytic enzymes by administering tetracyclines. The collagenolytic activity is manifested by excessive bone resorption, periodontal disease, rheumatoid arthritis, ulceration of cornea, or resorption of skin or other connective tissue collagen.
However, neither this nor U.S. Pat. No. 4,925,833 disclose nerve root injury or the treatment thereof.
It has also been disclosed that selective inhibition may be efficient in reducing sciatic pain (32).
Low back pain affects approximately 80% of the population during their lifetime in most countries. Except for being extremely common, it is also one of the most costly disorders for the society. In Sweden alone, low back pain was estimated to cost $320,000,000 in 1997. The major part of the cost relates to indirect costs such as sick-compensation and reduced productivity, and only a minor part is related to direct costs such as medical care and pharmacological substances.
In a minority of the cases (5%), there may be a known cause for the pain such as intra spinal tumors, rheumatic diseases, infections and more. In these cases the treatment may be specifically aimed at the cause. However, in the majority of the cases of low back pain, the cause remains unknown. At present there is no direct way to treat low back pain with an unknown cause and existing treatment modalities only aim at symptomatic relief.
Low Back Pain and Sciatica
It is necessary to make a distinction between low back pain and one specific condition that is often linked to low back pain called “sciatica”. Sciatica refers to radiating pain into the leg according to the dermatomal innervation area of a specific spinal nerve root. The pain in sciatica is distinctly different from that of low back pain. In sciatica, the pain is sharp and intense, often described as “toothache-like”, and radiates down into the lower extremities, below the level of the knee. The experience of the pain is closely related to the dermatomal innervation of one or more lumbar spinal nerve roots. Sciatica is also frequently related to neurological dysfunction in that specific nerve and may be seen as sensory dysfunction, reduced reflexes and reduced muscular strength. The sciatic pain thus seem to be a neuropathic pain, i.e. pain due to nerve injury, induced by sensitized axons in a spinal nerve root at the lumbar spinal level. The pain experienced by the patient as low back pain is more dull and is diffusely located in the lower back. There is never any radiating pain into the leg.
Sciatica is the result of nerve injury, and the cause of sciatica has an anatomical correlate. Since 1934, sciatica is intimately linked to the presence of a herniated intervertebral disc. However, although most patients with sciatica will display a herniated disc at radiological examination, it is surprising that approximately 30% of an adult population at the age of 40-50 years of age with no present or previous sciatica also have disc herniations when assessed by magnetic resonance tomography, so called “silent” disc herniations (8, 9, 10, 75). The presence of silent disc herniations is intriguing to the spine research community and seems to contradict the relationship between disc herniations and sciatica.
Scientific Knowledge of the Pathophysiologic Mechanisms Behind Low Back Pain
It is well known that the outer part of the annulus fibrosus of the intervertebral disc and the posterior longitudinal ligament are innervated by C-fibers. Although there are no nerve fibers in the deeper part of the annulus fibrosus or the nucleus pulposus in normal discs, nerves may reach these parts in degenerated discs through annular tears.
Silent Disc Herniations
As presented earlier, it is known that approximately one-third of a normal adult population who never suffered from sciatica have radiological visible disc herniations. Since the presence of a disc herniation is so intimately linked to the symptom of sciatica this is surprising, and at present there is no valid explanation for this phenomenon. However, “silent” in this regard only implies that the disc herniations did not produce sciatica. One may assume though that they produce other symptoms.
Whiplash and Whiplash Associated Disorders (WAD)
About 10% to 20% of the occupants of a stricken vehicle in rear-end car collisions suffer from whiplash injury. The injury may also occur as a result of other types of accidents, such as train accidents, and sudden retardations. This injury is defined as a non-contact acceleration-deceleration injury to the head-neck system. It is most often caused by a rear-end car collision and there is no direct impact on the neck.
Presenting symptoms usually include neckpain, headaches, disequilibrium, blurred vision, parenthesize, changes in cognition, fatigue, insomnia and hypersensitivity to light and sound. Dizziness described in a variety of terms such as imbalance, light-headedness and vertigo also occurs frequently and these symptoms may be associated with long-term disability.
Although neurologic and orthopedic examinations do not reveal abnormalities in the majority of patients, the characteristics of dizziness due to whiplash can be elucidated by means of ElectroNystagmoGraphic (ENG) evaluation. This examination is a method that is suitable for proving pathology in the oculo-vestibular system of whiplash-patients.
Until recently, the reason for the extent of injury was poorly understood. In addition, due to the legal and insurance issues, the veracity of complaints of neck pain and other symptoms by people who suffer from whiplash is commonly viewed as suspect.
Whiplash injuries can be quite complex and may include a variety of related problems, such as joint dysfunction, and faulty movement patterns, chronic pain and cognitive and higher center dysfunction.
When the cervical spine (neck) is subject to a whiplash injury, there is usually a combination of factors that contribute to the pain. These factors must be addressed individually, while maintaining a “holistic” view of the patient.
The most significant factors may include one or more of the following: joint dysfunction, muscle dysfunction, and faulty movement patterns.
Joint Dysfunction
This occurs when one of the joints in the spine or limbs loses its normal joint play (resiliency and shock absorption). It is detected through motion palpation, a procedure in which the doctor gently moves the joint in different directions and assesses its joint play. When a joint develops dysfunction, its normal range of movement may be affected and it can become painful. In addition, joint dysfunction can lead to a muscle imbalance and muscle pain and a vicious cycle. The loss of joint play can cause abnormal signals to the nervous system (there are an abundance of nerve receptors in the joint). The muscles related to that joint can subsequently become tense or, conversely, underactive. The resulting muscle imbalance can place increased stress on the joint, aggravating the joint dysfunction that already exists.
Muscle Dysfunction
When joint dysfunction develops, muscles are affected. Some muscles respond by becoming tense and overactive, while others respond by becoming inhibited and underactive. In either case, these muscles can develop trigger points. Trigger points are areas of congestion within the muscle where sensitizing compounds accumulate. These sensitizing compounds can irritate the nerve endings within the muscle and produce pain. This pain can occur in the muscle itself or can be referred pain (perceived in other areas of the body). Muscle related mechanisms may also give rise to abnormal signaling to the nervous system. This event can subsequently cause disruption of the ability of the nervous system to properly regulate muscles in other parts of the body, leading to the development of faulty movement patterns.
Faulty Movement Patterns
It is thought that the intense barrage of pain signals from a traumatic injury to the cervical spine can change the way the nervous system controls the coordinated function of muscles. The disruption of coordinated, stable movement is known as faulty movement patterns. Faulty movement patterns cause increased strain in the muscles and joints, leading to pain. They can involve the neck itself or can arise from dysfunction in other areas of the body such as the foot or pelvis. Instability is also considered part of faulty movement patterns. There are 2 types of instability that can occur in whiplash: passive instability-the ligaments of the neck are loosened, and dynamic instability-the nervous system disruption causes a disturbance in the body's natural muscular response to common, everyday forces. As a result of instability, even mild, innocuous activities can become painful.